My employer's Windows domain requires that account passwords must be changed every 45 days. Usually this necessitates booting a Windows machine on the domain (physical or in Parallels).

This morning I decided to VPN into the domain via my iPhone (v1.1.1) at home. I put in my regular password and received a prompt that my password had expired and the option to change it. (On 10.4 the login would fail.)

After submitting a new password, I updated my Mail settings to match the new password, and everything has been working great -- no Windows required.

I wonder if this is iPhone related or Leopard (based) related. OP, you mentioned Tiger, so maybe this works now on Leopard. Keys/Authorization works much differently it seems on Leopard and much better IMO - as an end-user anyway.